The present invention relates to motor vehicle seats including a height-adjusting mechanism, and to control devices for such seats.
More particularly, the invention concerns a vehicle seat comprising a seat part supported by a height-adjusting mechanism for adjusting the height of the cushion, the height-adjusting mechanism comprising:
at least one link member extending between, firstly, a first end adapted to be pivotally mounted in relation to the vehicle floor around a first pivot axis and, secondly, a second end connected to the seat part,
at least one control device comprising, firstly, a pinion which is rotatably mounted with respect to the seat part around an axis of rotation parallel to the first pivot axis, and, secondly, a rack which is pivotally mounted with respect to the seat part around a second pivot axis parallel to the first pivot axis, said rack being formed by a rigid plate having two principal faces perpendicular to the second pivot axis, said rack comprising a toothed section forming an arc of a circle centered on said second pivot axis and meshing with the pinion, and the rack being mechanically connected to the second end of the link member so that rotation of the rack around the second pivot axis is translated into rotation of the link around the first pivot axis.
Known seats of this type are generally satisfactory with regard to their operation under normal conditions, but present a risk of the pinion becoming disengaged from the rack when the vehicle is subjected to a violent shock in an accident. In that case, the control device violently releases the height-adjusting mechanism, so that the seat cushion is no longer suitably restrained by the vehicle floor, giving rise to risk of serious injury to the seat occupant.
The objective of the present invention is, in particular, to mitigate these disadvantages.
To meet this objective, according to the invention, the pinion is rotatably mounted inside a rigid yoke formed integrally with the seat cushion and comprising two rigid plates connected by a web, said two plates encasing the pinion substantially without free play along the second pivot axis and being arranged respectively against the two main faces of the rack, substantially without free play along said second pivot axis, in that each of the two plates has first and seconds end arranged on either side of the pinion, the first ends of the two plates being rigidly connected by mutual contact, outside the rack, to form the web of the yoke, and the second ends of the plates being connected by at least one fixing element passing through a slot forming an arc of a circle in the rack and centered on the second pivot axis, and in that the yoke has at least one stop which abuts radially on an arcuate abutment edge (arcuate meaning hereinafter: forming an arc of a circle) centered on said second pivot axis and formed in the rack, said abutment edge facing away from the toothed section of the rack.
As a result of these arrangements, the pinion is held in engagement with the rack in a particularly reliable way by the rigid yoke linking these two parts. This linkage is all the more reliable and robust because it is formed by only one intermediate part, i.e. the rigid yoke, over a generally short distance between the toothed section of the rack and the arcuate abutment edge of said rack, at the same time allowing the play between the pinion and the rack to be minimized and all intermediate parts which might reduce the mechanical strength of the assembly to be eliminated. In addition, if appropriate, the rigid yoke can be formed in a particularly compact manner, limiting both the weight and the cost of the height-adjusting mechanism.
In preferred embodiments, one and/or the other of the following arrangements could be used:
the second end of the link member is integral with the rack;
the second end of the link member is mounted pivotally on the rack;
the stop has an arcuate form complementary to that of the abutment edge;
each plate rests against the corresponding main face of the rack on either side of the slot in said rack;
the slot in the rack has a smooth arcuate edge forming said abutment edge, the second ends of the plates being in mutual contact and forming a rigid guide block engaging in said slot, this guide block having an outside edge forming said stop;
the slot in the rack is delimited between the abutment edge and the toothed section of said rack;
the slot in the rack has one edge which faces towards the second pivot axis and in which the teeth of said rack are formed, said rack having an outer edge forming said abutment edge, and the web of the yoke having an inner edge forming said stop;
the toothed section of the rack projects radially towards the outside of said rack, the rack having a recess forming an arcuate groove centered on the second pivot axis in one main face of the rack and an arcuate rib centered on the second pivot axis on the opposite main face of said rack, the second end of one of the plates having a relief projecting into the groove of the rack and resting radially at least against one edge delimiting said groove and facing away from the toothed section of the rack, and the second end of the other plate having an arcuate channel centered on the second pivot axis, said arcuate channel having one arcuate edge facing towards the toothed section of the rack and resting radially against an edge delimiting said rib, which edge of the rib faces away in from the toothed section of the rack;
the arcuate slot is formed in the recess of the rack; and
the height-adjusting mechanism comprises at least one transverse linking bar extending between first and second ends which are pivotally mounted on two lateral plates forming part of the cushion, the first end being integral with said rack and the second end being integral with an additional link which is intended to be mounted pivotally to the floor of the vehicle.